Multistage fan



Amrum, 1936. A. ESEELIG 2,037,395

MULTI STAGE FAN Filed April 26, 1935 2 Sheets-Sheet 1' l BY Slg 'l ATOR/VEY .i

m-pril 1.4, 1936.' A l A; E. sEELlG y l 2,037,395

MULTI STAGE FAN 11' ing Posop Cubic Feci zr Min v v:irmzrls'rnofn AN Aurea E. snug, New York, N. rf. Application anni ze, 1935, serial No.,1s,szs

15 Claims.

. This invention relates to propeller fans and particularly` to a load limiting air delivery pres- (cl. 23o-114) sure volume regulating means and combined following stage air guide vane to effectively multistage propeller fans.

Propeller fans are used in the art for varied purposes, as for example to supply air for fuel combustion in furnaces, for drying, for air oonditioning and for ventilation orv for vother uses where high volumes of air at relatively low static pressures are desired.

'I'he volume of air andthe pressure at which ow, the leading fan may then effectively react air delivery pressures, it is necessary to increase either the speed of rotation of the fan or its diameter, or both. It is apparent that, from a standpoint of mechanical design and the reduction of attendant noise of operation, it is not desirable to increase the diameter'ofthe fan and its rotational speed beyond certain limits.

In order,I therefore, to increase the delivery volume and pressures of such fans while at thel same time limiting the speed and diameter thereof, I` arrange aplurality of fans on a common drive shaft in series in a common conduit to thereby provide a multi-stage fan, having two or more stage fans, each succeeding fan to act as a booster for the .preceding fan.

ceding fan tothe following stage fan, that the following stage will thereby react and perform work on the air and to therebyincrease its forward velocity and thereby the volume and pressure at which it is finally delivered from the multi-stage fan.

The present invention, therefore, contemplates the provision of means whereby propeller fans may be effectively multi-staged. E,

I have found that by changing the motion of 10 the .air as it is delivered by the preceding fan from a forward rotational direction to a lforward direction parallel to the axis of the leading fan, without substantially reducing the speed of yair and perform work on the air so delivered to it, whereby the air volume and pressures delivered by such a multi-stage fan are substantially increased by each additional stage which is provided.

It will readily be understood that the magnitude of such forward rotational motion of the air delivered from a preceding fan may be varied, thereby varying the effectiveness of the following fan upon the air delivered 'to it and consequently varying the air volume and pressure delivered4 by the multi-stage fan as a unit.

A novel and simple pressure volume regulator for multi-stage fans may accordingly be arranged by providing means for varying the magnitude of the rotational motion of the air directed to In a propeller fan,4 the blades of which are l `stage fans, since each subsequent or following fan.

stage fan operates at the same speed and in the same rotative direction as the preceding stage fan, the column of air leaving the' preceding stage fan will have imparted to itl a rotary motion having substantially the same rotary speed and rotary direction as that of the following stage It will, at once, be seen that the following stage v fan can react only slightly or perform very'little workon the air delivered to it, and to `whip or push it forward, since both the fan and air are rotating in a similar rotative direction at substantialiy the same speed. -Itis readily apparent, therefore, that multi-staging the fans will not,

- of itself, result in the delivery of increased air propeller type fans may be varied by either changthe following stage fan, the provision of which the present invention further contemplates.

The volume of air and the pressure delivered by 35 ing the speed of rotationof the fan, by the use of a variable speed motor, or by maintaining a constant speed of rotation of the fan and restricting the air flow from the fan by means of a damper. l

Constant speed motors are simpler in construct on, more-dependable in operation and less costly than variable'speed motors, operating at high speeds, especially for use 4with alternating current', and the present invention is particularly directed tothe regulation of multi-stage propeller fans driven by constant speed electric motors;L

Since constant speed motors are mechanically more desirable to drive propeller fans, and there- 50 fore most frequently used in the art, regulation delivery side to thereby decrease the air volume 6c Reissue:

ing motor as the delivery volume is decreased.

since the increase in pressure on the delivery side of the fan, caused by the damper restriction,

produces an increased resistance to the rotation of theV fan. 'Ihe horsepower required to drive the fan increases as the volume of air is decreased under the influence of the damper, until the damper is entirely closed and air delivery ceases, when the horsepower. load on the driving motor is at a maximum.

It is apparent, therefore, 4that damper regulation of air supplied by constant speed motor driven propeller fans, heretofore generally found in the art, requires comparatively large capacity motors due to the fact that closing of the damper would overload the motor capacity selected to meet the requirement of maximum` air delivery with wide open damper.

The present-invention, therefore, further contemplates the provision of air volume regulating means for combination with constant speed motor driven multi-stage propeller fans, which, Within the predetermined air volume operating limits of the fans, provides a decreasing horsepower characteristic with decreasing volumes of air flow delivered and which regulating means -are arranged to limit the minimum air volume delivered and therefore the maximum horsepower load which can be placed on the driving motor.

The various objects of `my invention will be clear from the description which'follows and from the drawings in which Fig. 1 is-a| side elevation and partial section of my new multi-stage fan, showing the combined guide and pressure volume regulatingvanes.

Fig. 2 is a sectional view of the same taken on the line 2-2 of Fig. 1.

Fig. 3 is front sectional elevation, showing the guide vanes in fully closed position.

. Fig, 4 is a partial side elevation of my new multi-stage fan, andl guide vane regulating means.

Fig. 5 is a partial side elevation of a modification of my invention.

Figs. 6 fis a section taken on the line 6-6 of Fig.

Fig. 7 is a partial plan view of a further modification of invention.

Fig. 8 is a section on the line 8-8 of Fig. 7.

Fig. 9 is a front elevation of a modification of my novel guide vanes.

Fig. 10 is a graph oi' the pressure, volume and horsepower characteristics of a multi-stage fan constructed in accordance with my invention.

In that practical embodiment of my invention which I have illustrated by way of example in Figs. 1 to 4 inclusive, a constant speed electric motor III, for driving thelpropeller fans I2 and I4, is supported in the fancasing I6 on the motor cradle I8, which is secured to the casing in any suitable manner, as for example by means of bolts 20.

The motor shaft `22 extends from both sides of the motor body to receive the propeller fans,

as by a key and key way, well known in the art and which therefore need not be described in detail. v

It will be understood that: the motorffneed not be positioned intermediate the fans. but'may be positioned in any convenient place to drive the fans. as for example. outside the casing and operatively connected to the fans, either directly or indirectly, as by means of suitable gears or belts and pulleys.

As the motor drives the fans, air is drawn into the casing by the motion of the rstfan I2, which whips and pushes the air` before it imparting thereto a generally forward spiral motion, having substantially the same rotary direction as the fan I4. Since the following stage fan I4 is similar to the ilrst stage fan I2 and operates at the same speed, it will be apparent that the following stage fan does not effectively react or perform work on the air delivered to it and does not substantiallyimpart any further motion thereto since both the following fan and the air delivered toit rotate substantially in the same direction and at the samespeed.

In order therefore, to change the motion of guide or redirectional varies 2l, radially in the casing, adjacent to and on the discharge or delivery side of the first stage fan. The air, as it is delivered by the first stage fan, has imparted to it a substantially forward rotary motion with which it strikes the guide vanes, and flows therealong and is directed thereby axially toward the following stage fan. which can then more effectively react and perform work on the air stream directed to it.

Such guide or redirectional vanes may be constructed from sheet metal in the form of flat plates as shown in Fig. 1.

In order to prevent air -eddy currents, which may be produced by the flow of air against a flat plate, or any possible yresulting friction loss, streamlined guide varies 25, shown in Fig. 7, provided with proper curvature, whereby the direction of the air -flowing along the guide vanes may be gradually changed without formation of eddy currents or attendant friction loss may be supplied.

A If desired, such guide vanes may take the form of interlaced fiat plates or wires 26, as a honeycomb or egg crate, shown in' Fig. 9 or various other shapes.

The fans may be arrangedon the motor shaft as close together as the size of their common motor drive will permit-the guide vanes, preferably being arranged as nearly adjacent to the first stage fan as is possible.

It will be `apparent that the vdelivery eilectiveness of the` following fan on the air delivered to it is dependent on the magnitude of the rotational motion component of the air directed to the said following fan. It will be seen, therefore, that the air volume and pressure generated by the following stage fan, may be varied by varying the magnitude of the rotational motion of the air, prior to its delivery to the followl delivered by the multistage fan will therefore decrease.

It will at once be apparent that the magnitude of the rotational component mayl be increased by changing the position of the guide vane relatively to the following stage fan. whereby only a lower proportion of therair is'changed from the rotational direction as it leaves the rstfan.

Inorder,therefore.toprovideameansfor Cilv i aosases- -varying the proportion vof the delivered to the guide vanes in the casing sothat their posiytion relatively to the following stage fan may be changed to thereby vary the rotary component of the air directed to it.

Inasmuch as the following fan is less effective on the air directed to it and the work done by it on the air is less, as the rotary air delivery component is increased, it will be readily seen, that the motor horsepower required to drive the fans will decrease as the volume `is decreased and not increase as heretofore with. constant y speed damper controlled fans.

In order to vary the position of the guide vanes and to thereby regulate the air volume and pressure delivered by the multi-stage fan, I secure each guide vane to a shaft 21 which is pivotally `arranged. in a socket 28 arranged on the motor body, and thereby adapted to swing or rotate in the casing in the sockets.

- The vane shafts extend through suitable openings 30, arranged inthe casing, and are provided at' their upper ends with the horizontal arms 32, each having a pin'34 depending therefrom and engaging a slot 36, arranged on a sleeve 4a, which is adapted to be rotated on the casing thereabout.

In order to rotatably securethe sleeve onlthe casing, I prefer to arrange thereon a plurality of opposed pairs of Z bars 4|', the lower horizontal sides 42 of which are secured to the casing inv any suitable manner, suchas by rivets 44, and the upper horizontal sides 48 of the opposed Z bars together form an annular channel 41 in whichthe sleeve may be moved on the casing, the vertical sides 48, restraining the mofollowing fan axially thereof 'and the rotary` motion imparted to the air by the first fan, is

tion of the sleeve -to rotation about the casing.

A plurality of similar slots 36 are circumferentially arranged parallel to each other on the sleeve and divergently disposed to the axis thereof, each slot operatively engaging the pin depending from the horizontal vane arm and in which slot the pin may be urged-to reciprocate.

As the sleeve is rotated on the casing by the handle bar 5I, extending upwardly from the sleeve, the pin is urged to move in the slot, causing the shaft to rotate in the socket, and thereby changing the position of the vane relative to the first fan, or any following fan.

^ The slots are arranged to rotate the vanes from a full open position, when the vanes are disposed at right angles to the first fan, as shown in Fig. 2, in which position, air ilowing from the first fan is directed by the vanes toward the completely eliminated and the multi-stage fan delivers its. maximum capacity, to the full. closed position when the vanes are disposed parallel 'to the first fan, as shown in Fig. 3, in which position the multi-stage fan delivers its minimum capacity. y

The vanes are preferably arranged to `extend completely from the motor 'body to the .in'ner face 53 of the casing, the upper edges 4l, of the vanes, being preferably provided with a curvature similar to that of the casing. wherebythe upper vane edges-will lbe contiguous to the casing, when the vanesare in the full closed position.

In Fig. 10, I have shown a graph which `shows the-pressure, volume and horsepower character-` istics of a two stage fan constructed infacc'ordance with the present invention.

One series of curves is drawn to show the air ivolume in cubic feet per minute and the, corresponding pressures delivered by the two stage fan for' certain predetermined guide vane positions, which positions are diagrammati'cally illus trated at the right of the curves.

The pressure volume characteristic curves are indicated by the letters PV, thenumeral adjacent the letters signifying the corresponding. position of the guide vanes as illustrated at the right of the curves.

The second series'of curves are drawn to show the horsepower required to deliver the volume of air at the pressures shown on the iirst series of curves corresponding thereto for the given vane positions. These curves are indicated by the letters HP-V, the numeral adjacent the letters signifyingjhe corresponding position of the guide vanes. i

When the guide vanes are turned .to the full open, indicated as position 1, the pressure volume i fan characteristics are shown by the curve, PVl

andthe corresponding horsepower characteristics by the curve HP-Vl.

As the guide vanes are rotated in the casing to i horsepower (HPV3) characteristics are of a still lower magnitude.

vAs the guide vanes are still further rotated, to-

ward full closed position, into arbitrary position 4,

' in value and whenv the guide vanes assume a comlpletely closed position as indicated at 5, the horsepower (HPV5) will be greater than the maximum desired horsepower capacity, which would theref by overload the driving motor.

Hence, the present inventionfurther contem-` plates the provision of means' for limiting the maximum load which may be placed onthe motormulti-stage fan.. as the air volume is'.

driving my reduced.

For the purpose of illustration,l I will further 3, the magnitude of the rotary component of the describe my novel-multi-'stage fan and volume regulating means as applied to a coal burning boiler for supplying air thereto, though other apv lating purposes, will b e readily apparent to those skilled in the art.

'I'he thickness of the fuel bed, for which combustion air is to be furnished by my multi-stage fan, a sudden requirement for quick steaming in the boiler, or other conditions may require the supply by the fan of the volume of air at the pressure indicated at A on the curve PVl, which is obtainednwith the guide vanes disposed in full open position, the horsepower requirement for which will be found at A' on the curve IiP-V2. As the steam in the boiler is raised to the desired pressure, it will be apparent that the rate of fuel combustion must be lowered to a combustion rate which will maintain the boiler load, and the steam at the desired pressure, and therefore a lower air delivery volume is required. This may correspond vto the pressure volume characteristic B, to obtain which, it is readily seen requires the guide vanes to assume position 2 at which position the horsepower required is indicated at B'.

By further closing the guide vanes, it is readily seen that a lower pressure and volume C, with a corresponding lower horsepower C is obtained, until the dampering effect of the guide vanes is encountered, when the horsepower commences to increase, as indicated at D. It will be readily seen that as the dampering effect of the guide vanes increases air volumes and pressures are reached at which the horsepower increases until itv exceeds the maximum desired horsepower, namely the motor capacity.

It then becomes necessary to limit the reduction in the quantity of air delivered so that the motor will not be overloaded. The present invention therefore further contemplates the combination with the rotatable guide vanes of means for limiting themagnitude of the minimum air volume delivered and thereby limiting the load which may be applied to the motor drive. K

When the air passage is completely closed by the guide vanes, neither fan can deliver any air and the horsepower load on the driving motor will be at a maximum, and it will be understood that this maximum load may be avoided by arranging the guide vanes in such fashion thatthe entire air passage is never completely closed or restricted.

I accomplish such load llimitation byv constructing the guide vanesof a size such that, as the vanes are rotated into the full closed position, shown in Fig. 3, they arevappreciably spaced from each other, to provide the air release passages 50. The proportional total' area of these air release passages to the total area of the guide vanes may be varied as desired, but should be arranged to limit the pressure volume delivered when the guide vanes are completely closed to the magnitudes set forth at L cn the PV regulation curve, thereby limiting the load on the motor to the maximum desired horsepower.

'Ihe closure of the air passage may likewise be restricted by providing a stop pin 52 on the inner wall 5l of the casing, thereby limiting the rotation of the guide vanesand preventing the'casing area, or air passage, from being completely closed. 'Ihe positionof the stop pin will be determined from the pressure volume and horsepower characteristics of the particular fans to which the guidevanes are applied. as described above -It will be seen that my novel adjustable guide vanes redirect the air from the first stage fan toward any following stage to thereby effectively multi-stage a plurality of fans and provide a means for effectively regulating the volume of air v delivered by a multi-stage fan unit without overloading the motor driving the fans, by varying the magnitude of the rotational component of the air entering a following stage fan.

It will of course, be understood that the fan I2 may be omitted -to ythereby provide a simple or single stage fan having'adjustable guide vanes,` such as-shown in Figure 7, arranged adjacent the inlet side thereof, the surfaces of which vanes give to the air entering the fan a rotational and tangential component the magnitude of which may be varied by changing the positon of the guide vanes relative to the fan to thereby provide a novel volume pressure regulating means for a simple or single stage fan which will not overload the motor driving such fan as the volume of air delivered is decreased. l

Referring now to Figures 5 and 6, I have shown therein, a modification of the means for actuating my combined guide vanev and pressure volume regulating means.

In order to rotate the guide vanes 58, about the sockets 60 arranged on the motor body 62, I provide the radial shafts 64, fastened to the guide vanes, with the pinions B6 which are secured to the shaft ends 68, extending above the casing, through suitable openings 10 arranged thereon. The pinions operatively engage the annular rack gear 12, arranged on one face of the sleeve 1l, which is slidably arranged on the casing 16,

regulate the air volume and pressure delivered by the fans in the manner heretofore described. It will be understood, that a friction drive, belt and pulley, or any other suitable arrangement may likewise be used for my` novel fan air pressure and volume regulator.

It will be seen that I have provided a novel means for effectively multi-staging propeller fans,

and which means are adapted to provide pressure volume air regulation of said fans without overloading the motor driving the fans.

It will be further seen that I have also provided means for regulating the volume and pressure of the air delivered by a simple or single stage fan, which regulating means `will not overload the motor driving the fan as the air volume delivered is decreased.

While I have shown and described certain speciiic embodiments of my invention, it will be understood that I do not intend to limit myself thereto but desire to claim my invention as broadly as maybe permitted by the state of the prior art and thescope of the appended claims.

I claim: 1. The combination with a casing of a plurality of fans for generating a stream cf air arranged in the casing, means for driving the fans, the said stream of air having imparted thereto a generally forward rotational motion in the nature of a forward moving spiral by one of the said fans, and adjustable means intermediate the fans for selectively varying the rotational .motion of the air stream generated by onel of the said fans whereby air at predetermined volumeois delivered u fans decreases with decreased volumes of air delivered by the fans.

2. In combination, a motor, a multi-stage fan, air stream pressure volume regulating means for said multi-stage fan, said fan driven by said motor and said regulating means comprising a plurality of guide vanes adjustably arranged intermediate the fan stages, whereby the motor power required to drive the fans is directly proportional to the volume of air delivered.

3. In combination, a motor, a multi-stage faning, a plurality of fans arranged in the casing,

means for driving the fans, air volume regulating means comprising a plurality of guide vanes ro-v tatably secured to the casingintermediate the fans and gear means for rotating the guide vanes into selected positions whereby air at predetermined volumes vcorresponding to the position of the vanes is delivered by the fans.

5. In a multi-stage fan, the combination with I a plurality of fans, of means for driving the fans,

a guide vane rotatably arranged intermediate the fans and means for selectively positioning the guide vane relatively to the fans whereby air at predetermined volumes corresponding to the position of the guide vaneselected is delivered bythe fan and the power requirements ofthe fan `driving means is an increasing function of the lvolume of air delivered by the fans.

6. In a multi-stage fan, the combination with a plurality of fans for delivering air, one of the said fans imparting to the air delivered by it a rotational forward motion, of means for driving the fans and adjustable means adjacent said fan for variably adjusting the rotational component of the imparted air motion, before the air is delivered to the other fan, whereby the volume of air delivered by the multi-stage fan may be adjusted, said multi-stage fan having a decreasing horsepower characteristic with decreasing volumes of air delivered by the fan.

7.'In a device of the character. described, a casing, a plurality of fans arranged in the casing and rotating in the same direction, means for driving the fans, a plurality of guide vanes operatively arranged in the casing intermediate the -fans and adapted toI be selectively positioned therein and to thereby variably restrict the cas- -ing area, and means for operating the' vanes,

whereby the volume of air delivered may be adjusted selectively and the power requirements of and means for regulating the volume of air delivered by the fans including guide vanes adjustably arranged intermediate the fans and adapted to be positioned relatively to ,-the fans whereby the' motor horsepowerrequired to drive the fans decreases as the volume of air delivered by the fans is lowered by the selective positioning of the guide vanes.

9.l The combination with a casing of a plurality of propeller fans driven at constant speed arranged in the casing, means operatively connected to the fans for drivingthe fans and means for regulating the volume of air delivered by the fans, said volume regulating 'means being arranged intermediate the fans and adapted to be selectively positioned relatively thereto to thereby selectively regulate the volume of air delivered by the fans whereby the fan driving means horsepower decreases as the volume of air delivered by the fans is selectively decreased.

10. The combination with a casing of a plurality of propeller fans arranged in the casing, means operatively connected to the fans for driving the fans, means for regulating within a selected range the volume of air delivered by the fans, said volume regulating means being arranged intermediate the fans and adapted to be selectively positioned relatively thereto to thereby selectively yregulate the volume of air delivered by the fans whereby the fan driving means horsepower decreases as the volume of air delivered by the fans is selectively decreased.

11. The combination set forth in claim 10 and including means for limiting the position of the volume regulating means.

12. The combination with a plurality of propeller fans driven at constant speed of guide vanes adjustably arranged intermediate the fans, said vanes adapted to be selectively positioned relatively to the fans, to thereby provide means for regulating the volume of air vdelivered by the .fans whereby themotor horsepower required to drive the fans decreases as the volume of air dellvered by the fans is lowered by the adjustment of the guide .vanes, any selected position of the guide vanes corresponding toa predetermined air volume fan delivery.

13. In a device of the character described, a casing, a .plurality of fans arranged in the casing, a plurality ofguide vanes swingably secured the casing intermediate the fans, a sleeve rotatably arranged on the casing and. provided with a plurality of' slots and an arm secured to the guide vanes and engaging the slots, Awhereby the guide vanes are swung in the casing upon rotation of the sleeve on the casing.

14. In a device of the character described, a casing.' a plurality of fans arranged in the casing, a plurality of guide vanes swingably secured to the casing intermediate the fans, a.sleeve rotatably arranged on the casing, and means operatively connecting the sleeve and the guide vanes whereby the guide vanes are swimg in the'casing on rotation of the sleeve on the casing.

15. Ina device of the character described, a

casing, a plurality of fans-arranged in the casing, a plurality of guide vanes adjustably arranged in the casing intermediate thefans, .a

sleeve rotatably arranged on the casing and a linkage arrangement connecting the sleeve and the guide vanes whereby the guide vanes are adjusted in the casing on rotation of the sleeve on the casing.

ALFRED E. SEELIG. 

